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Glucose-to-fructose isomerization is the key process in the reaction sequence that can lead to the total conversion of biomass into valuable fine chemicals. However, it is challenging to find an efficient, cost-effective- and waste-minimized process to produce High Fructose Corn Syrup (HFCS) without using non-green approaches. To this end, hydrotalcite (MgAl-layered double hydroxides (MgAl-LDH)) catalyzed glucose isomerization in ethanol seemed to be one of the most promising processes in the last decade. In contrast to the well-studied reaction carried out in aqueous solutions, when ethanolic solutions are used, many potentially important properties of the LDHs cannot be studied in terms of how they affect their own catalytic abilities. Neither the effect of the basic site distribution, nor the morphological aspects and the role of surface hydration have been elucidated so far. In this study, the systematic alteration of the textural and structural parameters of hydrotalcites and hydrocalumites (Ca2Al-LDH) revealed clear structure–activity-selectivity relationships. These indicate that the rate-determining factor is the hydrophilicity and the LDH surface factors affecting it, which determine the catalytic performance of the LDH catalyst more than any other factor. This is evidenced by the fact that the catalytic efficiency of hydrotalcites can be improved by reducing their basicity. When isomerizations catalyzed by the easily recyclable LDH with suitable surface features are carried out, a truly similar catalytic performance (71% glucose conversion, 83% fructose selectivity, 59% fructose yield) can be achieved as was previously described, but at a significantly lower reaction temperature (120 °C → 80 °C). [ABSTRACT FROM AUTHOR]

Herein, we report novel catalytic methodologies for protodecarboxylations and decarboxylative deuterations of carboxylic acids utilizing a silver-containing hybrid material as a heterogeneous noble metal catalyst. After an initial batch method development, a chemically intensified continuous flow process was established in a simple packed-bed system which enabled gram-scale protodecarboxlyations without detectable structural degradation of the catalyst. The scope and applicability of the batch and flow processes were demonstrated through decarboxylations of a diverse set of aromatic carboxylic acids. Catalytic decarboxylative deuterations were achieved on the basis of the reaction conditions developed for the protodecarboxylations using D2O as a readily available deuterium source. [ABSTRACT FROM AUTHOR]

Here, we report on a one-pot mechanochemical ball milling synthesis of manganese oxide nanostructures synthesized at different milling speeds. The as-synthesized pure oxides and metal (Pt and Cu) doped oxides were tested in the hydrogenation of CO2 in the gas phase. Our study demonstrates the successful synthesis of the manganese oxide nanoparticles via mechano–chemical synthesis. We discovered that the milling speed could tune the crystal structure and the oxidation state of the manganese, which plays an essential role in the CO2 hydrogenation evidenced by ex situ XRD and XPS studies. The pure MnOx milled at 600 rpm showed high catalytic activity (∼20 000 nmol g−1 s−1) at 823 K, which can be attributed to the presence of Mn(II) besides Mn(III) and Mn(IV) on the surface under the reaction conditions. This study illustrates that the milling method is a cost-effective, simple way for the production of both pure, Pt-doped and Cu-loaded manganese nanocatalysts for heterogeneous catalytic reactions. Thus, we studied the Pt incorporation effect for the catalytic activity of MnOx using different Pt loading methods such as one-pot milling, wet impregnation and size-controlled 5 nm Pt loading via an ultrasonication-assisted method. [ABSTRACT FROM AUTHOR]

A new porosity determination method for nano- and sub-micron particles is proposed, which is based on single particle inductively coupled plasma mass spectrometry (spICP-MS) measurements. The performance of the new method was tested on core–shell Ag–Au, hollow Au and mesoporous SiO2 nanoparticles of different sizes and porosities and it was found that its accuracy and precision (e.g. 1–2 rel.%) are comparable to those of reference methods, such as small angle X-ray scattering (SAXS), gas adsorption or transmission electron microscopy imaging (TEM). It can be applied to nano- and submicron particles in the complete mesoporous pore (2–50 nm) range. The application to macroporous particles is also possible, but it is limited in size to particles that can be fully decomposed by the plasma. The proposed new spICP-MS method provides an advantageous set of features that is unparalleled among the porosity determination methods, namely (i) it only requires a very small amount of particulate sample (micrograms or even less) in the form of a dilute dispersion (e.g. in a 105 mL−1 particle concentration), so there is not even a need for a dry sample; (ii) it works for open and closed pores equally well; (iii) the measurement and calculation are quick and simple, and only need the external diameter of the particle (from e.g. electron microscopy or dynamic light scattering (DLS) measurements) as input. The overall porosity determined can also be used to calculate the density of the particles, a feat which is not easy to achieve from such a small amount of sample. [ABSTRACT FROM AUTHOR]

A nitrogen doped carbon aerogel was used as a substrate for the atomic layer deposition of TiO2 and ZnO layers in various thicknesses. The bare and composite products were analyzed using Raman spectroscopy, XRD, N2 adsorption, SEM-EDX, TEM, XPS, and ICP-OES and their photocatalytic activity was investigated in decomposing methyl orange dye under UV light irradiation. We investigated the effect of the different metal oxides and their thickness dependence on the photocatalytic activity. [ABSTRACT FROM AUTHOR]

The synthesis and characterization of a silver-containing hybrid material is reported as a novel heterogeneous noble metal catalyst. In order to eliminate the need for traditional immobilization techniques, and to create a solid material with structurally-bound silver catalytic centers, the layered structure of a naturally occurring mineral served as the basis of the initial catalyst design. The novel material was prepared by means of the urea-mediated homogeneous precipitation of the corresponding metal nitrates, and was fully characterized by means of diverse instrumental techniques (X-ray diffractometry, Raman, IR, UV-Vis, EPR, X-ray photoelectron spectroscopies, thermal methods as well as atomic force, scanning and transmission electron microscopies). The as-prepared material exhibited outstanding activity in silver-catalyzed C≡C bond activation to yield organic nitriles directly from terminal alkynes with less environmental concerns as compared to the classical synthesis methods. The effects of the reaction time, the temperature, as well as the role of various solvents, nitrogen sources and additives were carefully scrutinized in order to achieve high-yielding and selective nitrile formation. The heterogeneous nature of the reaction was verified and the solid catalyst was recycled and reused numerous times without loss of its activity or degradation of its structure, thereby offering a sustainable synthetic methodology. [ABSTRACT FROM AUTHOR]

In this study, the performance of five analytical techniques applicable to the determination of the load concentration of ultra small nanoparticles in a Pt/SiO2 nanocomposite was critically evaluated. Four of the techniques (SEM-EDS, TEM imaging, XPS and solution-mode ICP-MS) are often used for the characterization of nanoparticles, whereas single particle ICP-MS (spICP-MS) is an upcoming, novel methodology. After experimentally testing and discussing the pros and cons of each analytical technique, it was found that spICP-MS is one of the most accurate, precise and practical techniques for the analysis of nanocomposites. This technique works directly with dispersions, the measurement only takes a few minutes, it gives highly reliable results, largely free from interference from precursor residues and can also provide additional information about the particles. Although the individual measurement of ultra small nanoparticles is not yet possible by spICP-MS, the cumulative signal from such load particles in a nanocomposite allows the accurate determination of the load concentration. The spICP-MS result was concordant with the result obtained by TEM imaging, whereas SEM-EDS, XPS and solution-mode ICP-MS strongly overestimated the concentration. [ABSTRACT FROM AUTHOR]

Improving the catalytic activity of heterogeneous photocatalysts has become a hot topic recently. To this end, considerable progress has been made in the efficient separation of photogenerated charge carriers by e.g. the realization of heterojunction photocatalysts. V–VI–VII compound semiconductors, namely, bismuth oxyhalides, are popular photocatalysts. However, results on antimony oxyhalides [SbxOyXz (X = Br, Cl, I)], the very promising alternatives to the well-known BixOyXz photomodifiers, are scarce. Here, we report the successful decoration of titanium oxide nanostructures with 8–11 nm diameter SbxOyXz nanoparticles for the first time ever. The product size and stoichiometry could be controlled by the pH of the reactant mixture, while subsequent calcination could transform the structure of the titanate nanotube (TiONT) support and the prepared antimony oxychloride particles. In contrast to the ease of composite formation in the SbxOyXz/TiONT case, anatase TiO2 could not facilitate the formation of antimony oxychloride nanoparticles on its surface. The titanate nanotube-based composites showed activity in a generally accepted quasi-standard photocatalytic test reaction (methyl orange dye decolorization). We found that the SbxOyClz/TiONT synthesized at pH = 1 is the most active sample in a broad temperature range. [ABSTRACT FROM AUTHOR]

Scanning tunnelling microscopy (STM), low energy ion scattering spectroscopy (LEIS), X-ray photoelectron spectroscopy (XPS) and high resolution electron energy loss spectroscopy (HREELS) were applied for studying Au deposited on the Rh(111) surface. Both the deposition of Au at different substrate temperatures (400–800 K) and the effect of annealing Au deposited at 500 K were investigated. Gold deposition at 500 K, investigated by STM and LEIS methods, revealed that up to half monolayer Au the system exhibits clearly layer-by layer growth; however, above this coverage a slight deviation was identified, mainly due to kinetic and morphological effects. A continuous cover layer of Au was formed only above ∼2.5 monolayers (ML). Below this coverage, the pseudomorphic character of the Au overlayer was clearly proven by STM, but this feature disappears at 4 ML coverage. A moderate (5–10%) surface mixing of the two metals was observed only above 600 K, for both annealing the Au layer formed at lower temperatures and performing the deposition at elevated temperatures. Above 600 K a clear step-flow growth mechanism was verified. Depending on the Au coverage, a more extended mixing of the top layer and the sublayer was observed at even higher temperatures. In this case, nano-range ordering of the alloyed layer was detected by STM, where the lateral extension of the uniform commensurate (2 × 1) domains was around 4 × 4 nm2. In this case, the local intralayer mixing of Rh and Au can locally reach a value of 50%. The proposed structural model for the (2 × 1) alloy phase was also corroborated by HREELS investigations on CO adsorption. [ABSTRACT FROM AUTHOR]

The interaction of spatial concentration gradients with chemical reactions can lead to intricate precipitate patterns. When the density difference between the reactants is sufficient, gravity current forms at the reactive interface and solid particles can sediment along radially oriented thin lines if both nucleation and crystal growth are slow. In this paper, we have studied the flow-driven Co(ii)–oxalate system, by pumping cobalt nitrate solution into a thin layer of sodium oxalate solution. The formed precipitate consists of cobalt(ii) oxalate tetrahydrate, identified by thermogravimetric and X-ray diffractometric analysis. This simple flow method to maintain the spatial gradients represents a controlled synthesis resulting in microstructures significantly different from those obtained in well-stirred homogeneous experiments. [ABSTRACT FROM AUTHOR]

A quick and convenient approach that combines a printing process and chemical vapor deposition is developed for facile construction of nanostructured metal–carbon composite structures. Films of porous RANEY® nickel catalyst particles are deposited on various substrates by stencil printing from dispersions of the catalyst and poly(methyl methacrylate) in 2-(2-butoxyethoxy)ethyl acetate. After removing the organic binders at elevated temperatures, the mesoporous Ni film is applied as a growth template for synthesizing nanostructured carbon materials on the surface. Depending on the synthesis conditions, carbon nanofibers and nanotubes, as well as graphite deposits, are found to form on the substrates, allowing a robust and scalable production of carbon based inert electrodes of high specific surface area. In addition to structural characterization of the composites by means of scanning and transmission electron microscopy, Raman spectroscopy, X-ray diffraction, thermal gravimetric and surface adsorption analyses, the produced carbon/RANEY® nickel composites are also studied as electrodes in electrochemical capacitors (specific capacitance of ∼12 F g−1) and in field emitter devices with a low turn-on field (＜1.0 V μm−1). The results indicate the carbon/RANEY® nickel composites are suitable for direct integration on substrates used frequently in microelectronics. [ABSTRACT FROM AUTHOR]

Here, we report on a one-pot mechanochemical ball milling synthesis of manganese oxide nanostructures synthesized at different milling speeds. The as-synthesized pure oxides and metal (Pt and Cu) doped oxides were tested in the hydrogenation of CO2 in the gas phase. Our study demonstrates the successful synthesis of the manganese oxide nanoparticles via mechano-chemical synthesis. We discovered that the milling speed could tune the crystal structure and the oxidation state of the manganese, which plays an essential role in the CO2 hydrogenation evidenced by ex situ XRD and XPS studies. The pure MnOx milled at 600 rpm showed high catalytic activity (∼20 000 nmol g-1 s-1) at 823 K, which can be attributed to the presence of Mn(ii) besides Mn(iii) and Mn(iv) on the surface under the reaction conditions. This study illustrates that the milling method is a cost-effective, simple way for the production of both pure, Pt-doped and Cu-loaded manganese nanocatalysts for heterogeneous catalytic reactions. Thus, we studied the Pt incorporation effect for the catalytic activity of MnOx using different Pt loading methods such as one-pot milling, wet impregnation and size-controlled 5 nm Pt loading via an ultrasonication-assisted method.

Branched mesoporous silica SBA-15 materials have been prepared in a simple process using non-ionic surfactant in acidic conditions in the presence of metal ions.